Strip leveling apparatus



March 26, 1968 P. P. ZEIGLER 3,374,653

STRIP LEVELING APPARATUS Filed May 28, l 5 Sheets-Sheet l INVENTOR PAUL P. ZEIGLER ATTORNEY BY f j March 26, 1968 P. P. ZEIGLER STRIP LEVELING APPARATUS 5 Sheets-Sheet 2 Filed May 28, 1965 INVENTOR.

PAUL P. ZEIGLER ATTORNEY March 26, 1968 P. P. ZEIGLER 3,374,653

STRIP LEVELING APPARATUS Filed May 28, 1965 5 Sheets-Sheet IIO\ I08 m I02 E 6 INVENTOR.

PAUL P. ZEIGLER ATTORNEY March 26, 1968 P. P. ZEIGLER 3,374,653

STRIP LEVELING APPARATUS Filed May 28, 1965 5 Sheets-Sheet 4 50 H0 112' 0 Y o O 6 l 1 Q E I Q 8 INVENTOR.

PAUL P. ZEIGLER ATTORNEY March 26, 1968 P. P. ZEIGLER 3,374,653

5 TRIP LEVELING APPARATUS Filed May 28, 1965 5 Sheets-sheet 5 I NVENTOR.

PAUL P. ZEIGLER BY @621 ATTORNEY United States Patent 3,374,653 STRIP LEVELING APPARATUS Paul P. Zeigler, Spokane, Wash, assignor to Kaiser Aluminum & Chemical Corporation, Oakland, Calif., a corporation of Delaware Filed May 28, 1965, Ser. No. 459,743 14 Claims. (Cl. 72-161) ABSTRACT OF THE DISCLOSURE Apparatus for leveling continuously moving strip material and comprised of an improved arrangement of separate tension-inducing and bending rolls wherein a uniquely arranged pinch roll means is cooperatively associated with a tension-inducing roll so as to control in a precise fashion the tension applied to the strip by the tension-inducing roll.

This invention relates to an apparatus for continuously leveling a metal strip by permanently elongating the same a small amount so as to effect a uniform flattening of the strip across its entire width. While the invention is applicable to leveling different metals it is particularly suited to leveling long rolled strips of aluminum or aluminum alloys.

More particularly, the invention is concerned with an improved apparatus for continuously feeding metallic strip material along a sinuous path defined by a series of uniquely arranged tension inducing and bending rolls so as to produce a permanent flattening and elongation of the strip uniformly across its width.

In the past, cold rolling of metal strip has failed to produce an acceptable flat sheet or the like for many purposes and, accordingly, it has been necessary to supplement the rolling process with an additional flattening operation. A wide variety of equipment has heretofore been proposed and is in use today to accomplish the continuous stretching, flattening, leveling, etc. of metallic strip. The most common approach to the continuous processing of metallic strip has been to employ a complex arrangement of two or more driven rolls to accomplish the physical stretching and flattening of the metallic strip. These roll arrangements have lacked the flexibility required to flatten and level on the same equipment and with but minor adjustments a wide rangeof metallic strips which vary not only in width and thickness but also in metallurgical characteristics.

Accordingly, it is the primary purpose of the instant invention to provide a unique apparatus wherein a variety of metal strips can be continuously fed through a series of uniquely arranged tension inducing and bending rolls arranged so as to produce permanent flattening and elongation of a strip uniformly across its width.

This and other purposes and advantages of the instant invention will become more apparent from a review of the following detailed description when taken in conjunction with the appended drawings, wherein:

FIG. 1 is a diagrammatic side elevational View of a preferred embodiment of a stretcher-leveling apparatus;

FIG. 2 is a sectional view taken generally-along line 2-2 of FIG. 1 when rotated 90 counterclockwise and with certain parts removed;

FIG. 3 is a perspective view of a wiper assembly that can be utilized with the apparatus of FIGS. 1 and 2;

PEG. 4 is a sectional view along line 44 in FIG. 3 and illustrates the manner in which the wiper assembly of FIG. 3 can be mounted on the apparatus;

FIG. 5 is a partial diagrammatic and elevational view of one end of the apparatus shown in FIG. 1 and illus- 3,374,553 Patented Mar. 26, 1968 trates a second normal force producing arrangement for a driven roll;

FIG. 6 is a partial perspective view of the normal force producing pinch roll arrangement shown in FIG. 5 and illustrates further details thereof;

FIG. 7 is another partial diagrammatic and elevational view of the apparatus shown in FIG. 5 and discloses another species of a normal force producing arrangement adaptable for use with a driven roll;

FIG. 8 is a partial perspective view of the normal force producing arrangement shown in FIG. 7 and illustrates further details thereof;

FIG. 9 is a partial diagrammatic and elevational view of one end of the apparatus in FIGS. 1 and 2 and illustrates another normal force producing arrangement for use with one or more driven rolls; and

FIG. 10 is a partial diagrammatic and elevational view of the apparatus shown in FIG. 9 but with different upper and lower normal force-producing attachments.

With further reference to the drawings and in particular FIGS. 1 and 2, a preferred form of apparatus that can be used in canying out the teachings of the instant invention generally comprises a device 40 made up of frame members 4, 6, 8, 22 and a base generally indicated at 16 secured together in a suitable fashion such as by bolting. Mounted Within this framework is a series of rolls such as 10, 20 and 30 which are rotatably mounted thereto in a manner as will be subsequently described in detail. A strip of metal S preferably of aluminum or aluminum alloy of a suitable width and of relatively light gauge, on the order, for example, of .031" to .033", is unwound from payoflf reel 42 at the right end of the apparatus 40 in FIG. 1 and directed therethrough along a sinuous path by partially wrapping the same about the rolls in the manner shown in FIG. 1. As the strip exits from the apparatus 40 it can be wound about a rewind reel 44. Although the strip S is shown as being payed out from the reel 42, the strip S could also exit from a rolling mill or other type of strip processing means directly to apparatus The driven rolls 10 and 30 can be actuated by any suitable drive means, schematically indicated at M, such as a gear train, while bunker rolls 20 are not positively driven but are only idler rolls which are rotated by the strip itself. As will become more apparent hereinafter the driven rolls 1t and 30 cooperate by virtue of their alternate frictional engagement with successive opposite surface portions of the strip to incrementally place the strip along its entire width under suflicient longitudinal tension to exert a stretching force on the overall strip which preferably does not exceed its tensile yield point. To do this, the rolls 10 are driven at a slower rate than the exit tension rolls 30. To minimize slippage due to stretching the rolls 10 and the rolls 30 are preferably driven with graduated peripheral speeds. In passing through the driven rolls 10 the strip is preferably stretched to about its elastic limit. Then, in passing through the rolls 20 the strip is subjected to bending and stretching forces which result in permanent elongation of the strip S. Although five rolls 20 are shown, any number can be used. Thus the combination of both bunker rolls 20 and driven rolls 10 and 30 results in leveling the strip. The overall permanent stretch of the strip amounts to at least 0.75% relative elongation of the strip across its entire width and preferably it should be from l.0l.5% to level most widths of strip processed.

A significant feature in controlling the amount of tension which is applied by rolls 10 and 30 involves the use of one or more normal force producing means such as the pinch rolls '12 and 14 of FIG. 1. By normal force producing means is meant a means such as a roll or the like which applies a force in a direction normal to the planar face of the strip. These rolls 12 and 14 tangentially contact the strip and act to increase frictional forces applied to strip so as to increase the tension the desired amount all of which is dependent upon the particular gauge, width and metallurgical characteristics of the strip being processed.

Inasmuch as the stress range between the tensile yield point and the ultimate tensile strength for a given metallic strip is often relatively narrow some mean-s must be provided for adjusting the overall tension exerted by the various rolls 10, 20 and 30* whereby the ultimate tensile strength of the material will not be exceeded during the stretcher leveling operation. Although this can be done to some extent by changing the size and speeds of the various driven rolls 1% and 30 for each given strip of material being processed, this is obviously impractical in standard commercial operations. The use of normal force producing means such as pinch rolls 12 and 14, however, enables such an adjustment to be made easily by adjustment of the force the pinch rolls exert against the driven rolls and 30. I

With further reference to the embodiment of the invention shown in FIG. 1, the strip S has its surfaces partially wrapped around each driven roll 10 or 30 in such a fashion as to define a sinuous pathway of the strip therethrough whereby successive rolls of the apparatus 40 are in engagement with alternate opposing surfaces of the strip. As the strip S passes from one roll to another sufficient space is provided therebetween so that there is no biting engagement between adjacent rolls and the passing strip portion extending therebetween. The action of the entry and exit driven rolls 10 and 30 is merely to frictionally engage the strip S as it wraps around each roll 10 or 30. The circumferential extent of the strip S partially wrapped around each driven roll determines the amount of frictional engagement and with any compensations required being effected through use of the normal force producing rolls 12 and 14. 7

One suitable means for adjustably mounting either normal force producing roll 12 or 14 is shown in FIG. 9. Dependingly disposed intermediate the length of the frame member 8 is an additional frame member 50 which is rigidified such as by bracing members 52, to support an adjustable frame 54 for carrying the roll 12. The frame 54 comprises a carrier 56 that is slidably connected to the supporting frame member 50 by a series of rods 58, two of which are shown, that pass through lateral openings (shown as dotted lines) provided in the frame 50 in the usual manner. To controllably move the carrier 56 relative to the frame member 50 a fluid actuator 60 can be interconnected at its ends in a well known manner to the carrier 56 and a plate member 62 shown in cross section that constitutes part of the downwardly suspended frame member 50. By an appropriate hydraulic control circuit (not shown) the fluid actuator 60 can be extended or retracted to control the forceful engagement of the normal force producing roll 12 with the exposed surface of the strip S as it moves around the driven rolls 10.

To assure proper forceful engagement of the roll 12 with the exposed surface of the strip S, in order to increase the frictional drag on the strip S, the roll 12 is floatingly mounted to the carrier 56. To this end, a pair of link members'64, one of which is shown, are pivotally connected at their ends to the carrier 56 and to the shaft ends of the pinch rolls 12. To yieldably control the pivotal position of the link members 64 relative to the carrier 56, a pair of spring elements 66 are connected at their ends to the carrier 56 and link member 64 in the manner shown in FIG. 9 so as to provide a suitable yieldable means that permits the roll 12 to seek the proper position upon forceful engagement with the exposed surface of the strip S. a

By virtue of the aforedescribed attachment, the normal force producing roll 12 or 14 is capable of tangential engagement at two spaced lines along the exposed surface of the strip S as it wraps around alternate driven rolls such as 16 in FIG. 9. In other words, each. line of engage 4 ment by the pinch roll on the exposed surface of the strip S establishes a tangential line of contact that lies in a plane passing through the center of the underlying driven roll 10 or 30 and the center of the roll 12 or 14 as the 7 case may be. Thus it is evident that the normal force producing rolls 12 or 14, in controllable forceful engagement with the exposed surface of the strip S, can provide the additional frictional engagement of the strip S and driven rolls as aforedescribed whereby the strip S has the required longitudinal tension prior to the action of the bending rolls 20.

It is to be understood that all normal force producing rolls of the present invention preferably are of generally hollow construction wherein an outer metal-like cylindrical sleeve is connected at its ends to the roll shaft by a pair of circular end plates in the usual manner. The outer contacting surface of the sleeve can, if desired, be coated with a relatively soft grade of rubber or rubberlike material such as a suitable grade of neoprene rubber having a durometer scale reading in the range of 60-70. The purpose of having a relatively soft material on the normal force producing roll is to minimize any possible surface damage or a thickness reduction of the strip of material S.

Although not heretofore mentioned in connection with the description of FIG. 1, it is to be understood that the ends of the rolls 10 or 20 or 30 can be affixed in any suitable fashion at their ends to the frame members 4, 6 and 22 of the apparatus. To illustrate a typical connection, reference is drawn to FIG. 2 wherein, for the purpose of brevity, two driven rolls 10 and one freely rotatable roll 20 of FIG. 1 are shown in plan view and the general means by which they are affixed to the frame members 4 and 22. Appropriate block means 86 which are secured at their ends to the frame member 4 by cap screws generally indicated at 88 are provided with a transverse opening therethrough to mount in a suitable manner the shaft ends of each roll 10. Similarly, the freely rotatable roll 20 has a smaller block 86' that is aflixed in a similar fashion by the cap screws 88.

The driven rolls 10 or 30 are generally of a hollow construction similar to the aforedescribed hollow construction of a pinch roll but would differ therefrom to the extent they require a suitable drive means M as aforedescribed in connection with the description of FIG. 1. It is also desirable that the outer surface of the driven roll means 10 or 30 can be preferably coated with a relatively hard coating such as chromium. Such relative hardness assures, for all practical purposes, that the driven roll will notpick up any foreign material that will inadvertently do injury to the surface of the strip S as it wraps around each driven roll 10 or 30.

In the event that the driven roll 10 or 30 picks up any foreign material, an appropriate wiper means can'be provided to pick up and remove this material from the peripheral surface of the roll. With reference to FIG. 3 a wiper attachment 90 which produces no significant drag on the rolls is shown in perspective. It is adapted to be mounted to laterally extend between the frame members 4 and 6 at each end of the apparatus 40 in such a fash' ion that the attachment 90 is mounted in relation to one of the driven rolls so as to be disposed in operative relation to the exposed peripheral surfaceof the adjacent driven roll 10 or 30 (see FIG. 4). The wiper attachment 90 includes a one-piece rigid body'portion 96 having a downwardly extending lateral flange 97 intermediate the transverse width of the body portion 96. The longitudinal ends of the flange 97 include openings 99 therethrough for securely fastening, as subsequently described, the body portion 96 to one end of the blocks 86 aforedescribed for mounting the driven rolls 10 or 30. In other words, as shown in FIG. 4, cap screw 8-8 at one end of the block 86 passes first through the opening 99 in the flange 97 of the wiper body 96 and then through the cap screw opening inthe block 86 so as to rigidly fasten one end of the wiper attachment and the upper end of the block 86 to the frame member 4. Accordingly, the other end of the flange 97 is similarly fastened so that the wiper attachment 90 is afiixed in relation to the blocks 86 for mounting one driven roll while the wiper portion of the attachment 90 to be subsequently described is disposed in operative relation to the non-engaging peripheral surface of another laterally spaced but adjacent driven roll as illustrated in FIG. 4.

The wiper portion 92 has an overall T-shape such that the stem 93 is adapted to slidably fit into a closed end bore 95 that extends inwardly from an end of the body portion 96 and extends for substantially the longitudinal length of the body portion 96. The cap 93A of the wiper portion 92 opposite its connection with the stem 93 is inwardly recessed and has fixedly mounted therein an insert 94 that is made up of a suitable wiper material such that its outermost face is adapted to be in surfaceto-surface engagement with the non-engaging portion of the driven roll in FIG. 4. A series of adjusting set screws 98 are threadably passed through the end of the body portion 96 opposite the opening of the closed end bore 95. Adjustment of the set screws 98 effects advance ment of the wiper portion 92 into proper engagement with the surface of the driven roll 10. Thus, the wiper attachment 90 provides a simple means for assuring removal and pickup of foreign material that may cause injury to the strip S even though the peripheral surface of the driven roll 10 is provided with a relatively hard surface.

With reference to FIGS. 5 and 6 another embodiment of a normal force producing means is shown. The normal force producing means in this instance comprises a plurality of preferably identically sized pinch rolls 102 arranged in a cluster and freely rotatably mounted to a carrier assembly 104 such that all rolls 102 are arranged with their centers being located on an arc the radius of which emanates from the center of the driven roll with which the pinch rolls 102 are associated. The carrier as sembly 104 is pivotally connected in a similar fashion to a member 62', shown in section in FIG. 5, that con stitutes a part. of the intermediate frame member 50 aforedescribed in FIG. 9. The carrier assembly 104 comprises a pair of links 106, one of which is shown, pivotally connected at its ends to the lower end of the member 62' while the other end is pivotally connected to an arcuate shaped member 108, one of which is shown, that mounts the shaft ends of the pinch rolls 102 so as to be arranged in the clustered pattern shown. To control the angular position of the pivotally connected link member 106 a fluid actuator 110 is pivotally interconnected at its ends in a well known manner to the upper end of the member 62 and intermediate the length of the link member 106 so that upon extension or retraction of the fluid actuator 110 by an appropriate hydraulic circuit, not shown, the angular position of the link member 106 can be controlled. The arcuate shaped members 108 at each shaft end of the rolls 102 maintain a predetermined angular position with respect to the associated link member 106 by virtue of a pair of coil springs 112 that act as stabilizing means. To this end, a pair of springs 112 of suitable strength are interconnected at their ends to the link member 106 and the arcuate shaped member 108 in the manner shown in FIG. 6. Hence, when the fluid actuator 110 is extended for engagement of the pinch rolls 102 with the exposed surface of the strip as it wraps around the driven roll 10, the stabilizing action of the springs 112 enables angular adjustment of the arcuate shaped member 108 relative to the link member 106 so as to assure individual positive tangential engagement by each of the four normal force producing rolls 102 making up the cluster. Furthermore, it is to be understood that although only four rolls are shown, any number making up a cluster pattern can be provided. It is evident upon an inspection of FIG. 6 that the separate engagement of each of the rolls 102 with the exposed surface of the strip S is a similar tangential line of engagement as aforedescribed in connection with the roll 12 of FIG. 9 whereby each line of engagement is common to a plane that passes through the center of the driven roll 10 and the center of the engaging roll 102.

Referring to FIGS. 7 and 8, another normal force producing means comprising a belt wrapping device is shown pivotally connected to the outer end of the link member 106 of the carrier assembly 104 in FIG. 5. This device 105 includes a pair of spaced rolls 114 preferably of identical size that are mounted to a carrier member 116 constituting a rigid frame made up of a series of elongated plate members such that each end of the carrier member 116 is the configuration shown in FIGS. 7 and 8 whereby the carrier member 116 laterally extends between the shaft ends of the rolls 114. The shaft ends of the rolls 114 are desirably freely rotatably mounted to the ends of the forwardmost projecting members making up the carrier member 116. A normal force producing means such as an endless belt member 118 of a suitable flexible material is adapted to be wrapped around the rolls 114 so as to extend therebetween in FIGS. 7 and 8 but in such a fashion that the upper run of the belt member 118 can be partially wrapped around the exposed surface of the strip S as it moves around the driven roll 10 in FIG. 7. In other words, when the upper run portion of the belt 118 extending between the spaced rolls 114 is pressed against the exposed surface of the strip S the flexible material of the belt member 118 accommodates itself to the contour of the exposed surface of the strip S so as to be in surface-to-surface engagement therewith. This engagement by virtue of the fact that the rolls 114 are rotatably mounted to the carrier 116 results in a movement of the belt member 113 corresponding to the line speed of the strip S.

To stabilize the angular position of the carrier member 116 coil springs 112 are connected at their ends to extend between the carrier member 116 and the link memher 106. Thus, when the fluid actuator is actuated by a hydraulic control circuit, not shown, in a well known manner, the intermediate portion of the upper run of the belt member 118 can be pressed into forceful engagement so as to partially wrap itself around the exposed surface of the strip S as the opposite surface of the strip S wraps itself around the associated driven roll 10. Such forceful engagement increases the overall frictional contact between the engaging surfaces of the strip S and the peripheral surface of the driven roll 10.

In FIG. 10 a pair of normal force producing rolls 70 can be mounted for tangential engagement with the exposed surface of the strip S as it is wrapped around successive driven rolls 10. Accordingly, the lower roll 70 at its longitudinal ends is connected to the upper end of a lever 120 of obtuse angular shape one of which is only shown. The lever 120 is pivotally connected intermediate its ends to the frame member 4 while the lower end is pivotally connected to the rod of a fluid actuator 122 and the body portion thereof is pivotally connected to a bracket member 124, shown in cross section, that constitutes a part of the frame 4. Similarly, the upper roll 70 is pivotally connected to a lever 126 of right angle shape that is pivotally connected intermediate its ends to the upper frame member 8. The upper end of the lever 126 is pivotally connected to the extensible rod of a fluid actuator 128 and the body portion thereof is pivotally connected to a bracket member 130 shown in cross section, that is a part of the frame 8. Thus, the pinch rolls 70 by virtue of the fluid actuators 122 and 128 can be separately adjusted into engagement with successive driven rolls 10 to thereby control the frictional engagement of the strip S with the set of driven rolls 10.

It is apparent from the above description that various changes and modifications may be made without departing from the invention. Accordingly, the scope of the in- 7 vention should be limited only by the appended claims, wherein:

What is claimed is:

1. An apparatus for leveling and flattening a metal strip, comprising the combination of a frame, a plurality of strip engaging and tension-inducing rolls rotatably driven and mounted on the frame and forming a sinuous path of travel for the strip, normal force producing means comprised of a strip driven pinch roll mounted on said frame in cooperative relationship to at least a pair of said tension-inducing rolls and adapted to frictionally grip the strip adjacent said pair of tension-inducing rolls and thereby create a preselected tensional stress in a portion of the strip disposed between certain of the rolls in said plurality of tension-inducing rolls, and means for moving said pinch roll into seating relationship between said pair of tensioninducing rolls and into engagement with the surface portions of the strip opposite to those engaged by the said pair of tension-inducing rolls.

2. An apparatus for leveling and flattening a metal strip, comprising the combination of a frame, a plurality of strip engaging and tension-inducing rolls rotatably driven and mounted on the frame and forming a sinuous path of travel for the strip, normal force producing means mounted on said frame in cooperative relationship to at least one of said tension-inducing rolls and adapted to frictionally grip the strip and thereby create a preselected tensional stress in a portion of the strip disposed between certain of the rolls in said plurality of tension-inducing rolls, means for moving said normal force producing means into engagement with the surface portion of the strip opposite to that engaged by said one of the tensioninducing rolls, and said normal force producing means being comprised of a strip driven endless belt means disposed adjacent said one of the tension-inducing rolls and said belt means being adapted to partially envelope the strip in contact with the said one of the tension-inducing rolls with which the endless belt means is associated.

3. An apparatus for leveling and flattening a metal strip, comprising the combination of a frame, a plurality of strip engaging and tension-inducing rolls rotatably driven and mounted on the frame and forming a sinuous path of travel for the strip, normal force producing means mounted on said frame in cooperative relationship to at least one of said tension-inducing rolls and adapted to frictionally grip the strip and thereby create a preselected tensional stress in a portion of the strip disposed between certain of the rolls in said plurality of tension-inducing rolls, means for moving said normal force producing means into engagement with the surface portion of the strip opposite to that engaged by said one of the tensioninducing rolls, said normal force producing means comprising a cluster of strip driven pinch rolls disposed adja cent the said one of the tension-inducing rolls and adapted to engage an exposed surface of the strip as it is wrapped about the said one of the tension-inducing rolls with which the pinch rolls are associated and means apart from said pinch rolls for directing the strip away from the said one of the tension-inducing rolls.

4. An apparatus for leveling and flattening a metal strip, comprising the combination of a frame, a plurality of strip engaging and tension-inducing rolls rotatably driven and mounted on the frame and forminga sinuous path of travel for the strip, normal force producing means mounted on said frame in cooperative relationship to at least one of said tension-inducing rolls and adapted to fn'ctionall-y grip the strip and thereby create a preselected tensional stress in a portion of the strip disposed between certain of the rolls in said plurality of tension-inducing rolls, means for moving said normal force producing means into engagement with the surface portion of the strip opposite to that engaged by the said one of the tension-inducing rolls and a wiper attachment mounted on said frame and disposed in operative relation to the exposed peripheral surface of a tension-inducing roll. p 1

5. An apparatus for leveling and flattening a metal strip, comprising the combinationof a frame, groups of strip tension-inducing rolls rotatably mounted "on the frame and forming a sinuous path of travel for the strip, a bending roll disposed between successive groups of said tension-inducing rolls, normal force producing means mounted on said frame in cooperative relationship to at least one of said tension-inducing rolls in a group of said tension-inducing rolls, means for driving the rolls in,

one group of tensiondnducing rolls at different peripheral speeds from the rolls in another group of tension-inducing rolls so that said tension-inducing rolls'in the, successive groups of said tension-inducing rolls are adapted to frictionally grip the strip and thereby create a'preselected tensional stress in the strip disposed between the said groups of said tension-inducing rolls and means for moving said normal force producing means into pinching engagement with the surface portion of the strip'opposite to that engaged by the tension-inducing roll with which the normal force producing means is associated to thereby increase the frictional contact between the strip and said last mentioned tension-inducing roll so as to selectively augment the tensional stress induced in the strip by said last mentioned tension-inducing roll and while minimizing a thickness reduction in the strip and with said bending roll being adapted to effect a further stretching and a permanent elongation of said strip within selected limits.

6. An apparatus as set forth in claim 5' wherein said bending roll is driven by said strip.

7. An apparatus as set forth in claim 5 wherein the tensioninducing rolls in a given group of rolls are driven at graduated peripheral speeds from the entry to the exit end of said group.

8. An apparatus for leveling and flattening a metal strip comprising the combination of a frame, groups of strip tension-inducing rolls rotatably mounted on the frame and forming a sinuous path of travel for the strip, a series of bending rolls interposed between said groups of strip tension-inducing rolls, normal force producing means mounted on said frame and disposed in cooperative relationship adjacent at least one of said tensioninducing rolls in a group of said tension-inducing rolls, means for driving the rolls in one group of said tensioninducing rolls at different peripheral speeds from the rolls in another group of tension-inducing rolls so that said tension-inducing rolls in said groups of tension-inducing rolls are adapted to frictionally grip the strip and there by create a preselected tensional stress in the strip dis posed between the separate groups of said tension-inducing rolls, and means for forcing said normal force pro- 7 ducing means into pinching engagement with the surface portion of the strip opposite to that engaged by the tension-inducing roll with which the normal force producing means is associated to thereby increase the frictional contact between the strip and said last mentioned tensioninducing roll so as to selectively augment the tensional stress induced in the strip by said last mentioned tensioninducing roll while minimizing a thickness reduction in the strip and to effect a permanent elongation of said strip within selected limits. V i p 9. An apparatus as set forth in claim 8 wherein said normal force producing means comprises a strip driven pinch roll. i

10. An apparatus for leveling and flattening a metal strip comprising the combination of a frame, groups of strip tension-inducing rolls rotatably mounted on the frame and forming a sinuous path of travel for the strip, normal force producing means mounted on said frame and disposed in cooperative relationship adjacent at least one of said tension-inducing rolls in a group of said tension-inducing rolls, means for driving the rolls in one group of said tension-inducing rolls at ditferentperipheral speeds from the rolls in another group of tension-inducing rolls so that said tension-inducing rolls in said groups of tension-inducing rolls are adapted to frictionally grip the strip and thereby create a preselected tensional stress in the strip disposed between the separate groups of said tension-inducing rolls, means for forcing said normal force producing means into engagement with the surface portion of the strip opposite to that engaged by the said one of the tension-inducing rolls with which the normal force producing means is associated to thereby increase the frictional contact between the strip and said last mentioned tension-inducing roll so as to selectively augment the tensional stress induced in the strip by said last mentioned tension-inducing roll and to effect a permanent elongation of said strip within selected limits, and said normal force producing means comprising a strip driven endless belt means disposed adjacent the last mentioned tension-inducing roll, said belt means being adapted to partially envelope the strip in contact with said last mentioned tension-inducing roll.

11. An apparatus as set forth in claim 8 wherein said normal force producing means comprises a cluster of strip driven pinch rolls disposed adjacent a tension-inducing roll and adapted to engage the exposed surface of the strip as it is Wrapped about the tension-inducing roll.

12. An apparatus as set forth in claim 5 wherein said normal force producing means comprises a strip driven pinch roll insertable between a pair of tension-inducing rolls.

13. An apparatus as set forth in claim 5 wherein said normal force producing means comprises a strip driven endless belt means disposed adjacent the said one of said tension-inducing rolls and adapted to partially envelope the strip in contact with the last mentioned tension-inducing roll.

14. An apparatus as set forth in claim 5 wherein said normal force producing means comprises a cluster of strip driven pinch rolls disposed adjacent the said one of the tension-inducing rolls and adapted to engage the exposed surface of the strip as it is Wrapped about the last mentioned tension-inducing roll.

References Cited UNITED STATES PATENTS 2,332,796 10/ 1943 Hume 72l60 2,504,292 4/ 1950 Anderson 72164 2,526,296 10/ 1950 Stone 72-164- 3,25 3,445 5/ 1966 Franck 72164 CHARLES W. LANHAM, Primary Examiner. RONALD D. GREFE, Examiner. 

